The invention relates to a card reader with three feed rollers mounted on pivot arms and which are serially disposed in the direction of card insertion, the pivot arms being coupled for movement with one another and being pivotable in a plane at right-angles to the card path against the action of a restoring force and whereby the feed roller which is at the rear in the direction of insertion is disposed on a rear pivot arm behind its pivot axis and in that the feed roller which is in front in the direction of insertion is disposed on a forward pivot arm in front of its pivot axis.
Such a card reader is known for example from DE 200 02 405.1 U1.
This prior art card reader comprises three feed rollers disposed one after another in the direction of card insertion and also two pivot arms which are pivotable in each case in a plane at right-angles to the card path and against the action of restoring springs. Between their pivot axes, the two pivot arms are connected to each other articulatingly via a common pivot axis and are therefore coupled together for movement in opposite directions. The feed roller which is in front and that which is behind in the direction of insertion are in each case mounted on the free end of the two pivot arms whereas the middle feed roller is mounted to rotate about the common pivot axis. When the card is being driven by the middle feed roller, the other two feed rollers are raised by more than the thickness of the card and are therefore pivoted completely out of the card path. Driven solely by the middle feed roller, the card is able to pass by a write/read head for data exchange without the other two feed rollers hampering this movement.
The lever ratio of middle to rear feed roller in the case of the known card reader amounts to 1:3.5, i.e. for a middle feed roller travel of 1 mm, the travel of the rear feed roller amounts to approximately 3 mm. In the case of a given pressure weight of the middle feed roller on its mating roller of 1000 g, the pressure weight of the rear feed on its mating roller amounts to only about 300 g. In the case of cards which are transversely curved, i.e. about their longitudinal central axis, this minimal weight of pressure of the rear feed roller is insufficient to ensure trouble-free feed of the card by means of the rear feed roller.
In the case of a card reader of the type mentioned at the outset, the problem on which the invention is based is that of enhancing the pressure weight which acts on an inserted card by the rear feed roller.
According to the invention, this problem is resolved by two middle pivot arms which are articulatingly connected to each other, one middle pivot arm being, at a distance from its pivot axis, connected articulatingly to the rear pivot arm while the other middle pivot arm is articulatingly connected to the front pivot arm at a distance from its pivot axis.
The advantage achieved by the invention resides in the fact that a lesser lever ratio of middle to rear feed roller of for example 1:1.5 can be achieved. In this exemplary case, in the case of a travel by the middle feed roller of 1 mm the travel of the rear feed roller is about 1.5 mm and for a given weight of pressure of the middle feed roller on its mating roller of 1000 g, the pressure weight of the rear feed on its mating roller is about 750 g. As a result of this high weight which is applied by the rear feed roller, perfect transport is ensured by means of the rear feed roller even in the case of cards which are tremendously transversely curved.
In the case of particularly preferred embodiments of the invention, the two middle pivot arms are articulatingly connected to each other between the pivot axes of the rear and of the front pivot arms. In this respect, the middle feed roller is mounted between the pivot axes of the front and of the rear pivot arm and in fact either only on one of the two middle pivot arms or on both middle pivot arms about the axes of rotation of their articulating connection.
Preferably, a read and/or write head of the card reader is provided in the region of the middle feed roller. This measure has the advantage that, driven only by the middle feed roller, the card can be passed by the read and/or write head equally in both directions and with a clearly defined application pressure.
The restoring force can be constituted for example by one or more restoring springs acting in each case on articulating connections between the pivot arm and/or on restoring springs acting on feed rollers so that the feed rollers are initially tensioned in their positions which engage the card path.
Preferably, only a single restoring spring is provided which is at the bottom biased on the pivot axes of the pivot arms and at the top bears on the pivot axes of the articulating connections of the rear and front pivot arms as well as on the rear and front feed roller. To this end, a restoring spring constituted by one wire is threaded in between the axes of the feed rollers, pivot arms and articulating connections.
Furthermore, on the side of the card path which is opposite the feed rollers, in each case one mating roller is associated with each feed roller as a mating mounting for the card which is to be transported.
Further advantages of the invention will arise from the description and from the drawings. Equally, the aforementioned and features which still have to be mentioned are in accordance with the invention capable of being used individually, by themselves or in any desired combination. The embodiments shown and described are not to be understood as a conclusive enumeration but rather more have a character of exemplifying the invention.